Process of filling discharge tubes constructed without exhaust tube

ABSTRACT

The process relates to filling exhaust tubeless cylindrical lamp bulbs having no exhaust tubes - so called ceramic lamps or discharge tubes - with discharge substances as well as to the sealing of same. A cup containing a mixture which upon heating liberates metal vapor is fixed to an electrode, the latter one is introduced into and united with a ceramic cup. After this, this whole assembly is introduced into and sealed by means of a glasslike binder to the ceramic bulb which is preferably made of aluminum oxide. The reaction mixture contained in the cup is heated thereafter.

United States Patent 15 3,650,593 Kerekes [4 1 Mar. 21, 1972 [54] PROCESS OF FILLING DISCHARGE 2,460,739 2/1949 Francis ..313/1s4 x TUBES CONSTRUCTED WITHOUT 3,303,377 2/1967 Jansen et a1. ..313/184 3,385,463 5/1968 Lange ..3l3/220 UX EXHAUST TUBE 3,390,296 6/1968 Smith ..3l3/220 UX [72] Inventor: Bela Kerekes, Budapest, Hungary FOREIGN PATENTS OR APPLICATIONS [73] Assignee: Egyesult Izzolampa es Villamossagi Reszvenytarsasag, Budapest upjert Hungary 502,321 3/1939 Great Britain ..3l3/184 [22] Filed: Oct. 21, 1969 Primary Examiner-John F. Campbell Assistant Examiner-Richard Bernard Lazarus [2]] Appl' 8681l6 AtIorney--Arthur O. Klein [30] Foreign Application Priority Data ABSTRACT Nov. 22, 1968 Hungary ..EE 1596 The process r es to filling exhaust tubeless cylindrical lamp bulbs having no exhaust tubes so called ceramic lamps or 52 US. Cl ..316/4, 313/220, 316/3 discharge tubes w discharge Substances as well as to the 51 111:. c1. ..H01j 9/18, 1101 j 9/38 Sealing of A P Containing a mixture which P heat- [58] Field of Search ..316/3, 13, 4; 313/184, 220 mg liberates metal vapor is fixed electwde, the latter one is introduced into and united with a ceramic cup. After this, 5 R f d this whole assembly is introduced into and sealed by means of 6] e erences Cl 0 a glass-like binder to the ceramic bulb which is preferably UNlTED STATES PATENTS made of aluminum oxide. The reaction mixture contained in the cup is heated thereafter. 2,012,237 8/1935 Beck .....3l6/l3 X 2,087,735 7/1937 Pirani et al ..3l3/184 X 5 Claims, 1 Drawing Figure Patented March 21, 1972 3,650,593

I NVENTOR I Bela KEREKES BYI ATTORNEY This invention relates to a process for filling and sealing so called ceramic lamps or discharge tubes with discharge substance.

In the last few years, sodium-metal discharge lamps have become known on an ever increasing scale. One reason for this resides in the high efficiency of lamps of this kind. If the lamp bulb is made of translucent sintered aluminum oxide, in addition to its good efficiency, the light radiated by the lamp can be made more pleasing to the human eye. The latter metal-vapor discharge lamps are known as ceramic lamps.

It is well known that the vacuum-tight sealing of these ceramic lamps is a difficult problem of production engineering. There are a number of reasons for this. One derives from the usual problem referred to conventionally as evacuation method. The known method of evacuating lamp bulbs is carried out in fact by means of a so-called exhaust tube. Consequently, the use of an exhaust tube has to be taken into consideration in the construction or design of these ceramic lamps. The exhaust tube, however, can be made only ofa special metal, i.e., a metal which is sufficiently resistant to the vapor of alkali metals (for example sodium vapor). The metal of the exhaust tube, however, has also other technical and physical conditions to meet. Thus, for example, it is important that the material of the exhaust tube should be weldable when cold; furthermore, it should be economically machinable. The thermal expansion of the metal should be such that no stresses will be set up in the fitted tube which could cause any fissures or cracks and fracture, and so forth.

According to US. Pat. No. 3,243,635, it is proposed to use niobium for the aforesaid purpose. This niobium body is fused to the material of the tube, for example by means of a special glass (for example, according toBritish Pat. No. 961,670), the coefficient of thermal expansion of this glass matching that of the tube and the niobium. Another solution of the problem is described in US. Pat. No. 3,385,463, in which 90 percent of the binder is A1 while the remaining percent of alkaline earth metal oxides or gallium oxide, beryllium oxide, magnesiurn oxide. In other solutions, for example according to British Pat. No. 1,065,025, a barrier layer of titanium, zirconium, vanadium or hafnium is used, for example.

The material of the exhaust tube may be for example stainless steel or even an iron-nickel-cobalt alloy of iron, in which case, however, especially at elevated temperatures, hard soldering, sealing thereof, etc., is comparatively difficult to carry out.

The aim of our invention is to improve the technical situation which has been described above by overcoming the aforementioned difficulties.

The invention concerns a ceramic lamp and corresponding filling process, in which no exhaust tube is used, and in which no such tube is provided.

As is well known, products to be regarded as typical vacuum engineering products, such as, for example, incandescent lamps, discharge tubes and so forth, are provided with exhaust tubes. Exhaust or evacuation of the air from the lamp bulb takes place through this exhaust tube, and the same exhaust tube is used for filling the lamp bulb with the discharge substance necessary for the operation of the lamp.

In the case of a glass or quartz bulb, the situation is relatively simple. In the case of discharge tubes, however, the bulbs of which consist of translucent aluminum oxide, the exhaust tube, as already outlined, cannot be made of aluminum oxide, that is to say, therefore, of the material of the bulb if it is necessary to combine together the sealing of the bulb and the application of the exhaust tube, in which case the aforesaid difficulties arise.

In metal vapor discharge tubes of conventional construction, the omission of the exhaust tube would render difficult the introduction or supply of the principal discharge substance, i.e., the alkali metals, into the discharge tube. Accordingl to the invention, therefore a solution is proposed, which is ot erwlse known, and In which the production of the alkali metal is carried out within the bulb itself by means of a chemical process. There is therefore provided within the bulb, in manner known per se, a mixture of those chemical compounds, for example in a metal capsule, from which mixture under the effect of heat alkali metal vapor is liberated for the discharge mechanism. The material mixture may, of course, also be provided in a closed metal capsule in which process the material is liberated by high-frequency heating after fusion of the metal capsule.

The invention will now be described by way of example and with reference to the accompanying drawing.

The sole figure of the drawing is the view partially in axial section and partially in elevationof a ceramic lamp made according to the invention.

In the drawing the ceramic tube 4 shown is provided with the cathodes l, and then the cap 6 is fixed to the ceramic tube by means of the glass-like binder 5. The also glass-like binder 7 secures'both the cap 6 and the electrode 8. As will be seen from the figure, fixed to the electrode 8 is the cuplike container 3 carrying the reaction mixture 2. In the case of sodium lamps, for example, this substance may be a mixture of sodium lamps, for example, this substance may be a mixture of sodium tungstate and zirconium powder.

Final sealing of the bulb is preferably carried out by heating the binder 5 by radiant heat until it melts, the tube being allowed to fall under its own weight into the cap 6, a xenon pressure 20-60 mm. Hg, which assists ignition of the lamp, being left at room temperature in the interior of the bulb.

This source of sodium simplifies the difficulties of supplying the discharge substance, because by its use sealing of the bulb may be effected without the use of an exhaust tube. Handling of the chemical compounds is easier, since the alkali (sodium) compounds to be reduced are stable in the air.

Of course, a number of metal compounds, for example, sodium and cesium or other metal compounds known in lamp technology, may be reduced simultaneously in admixture. These metals or their mixtures, possibly their alloyswe are here thinkingmainly of the alkali metals -may also be sealed airtight in metal capsules and thus introduced into the bulb 4, in which case by melting the metal capsules by means of high frequency the metals maintaining the discharge may be vaporized from the mixture or the alloys.

The product made by the process naturally also forms the subject of the invention.

What we claim is:

l. A process of filling a lamp adapted for operation at high temperature and provided with a cylindrical ceramic bulb without an exhaust tube with the discharge substances, comprising introducing an inert atmosphere at a pressure of 20-60 mm. Hg into the bulb before sealing it from the atmosphere, introducing an electrode and a cup containing a mixture which liberates metal vapor into a hole in a ceramic cap for the ceramic tube, uniting the cap to the electrode by a glasslike binder, introducing the electrode into the ceramic bulb, airtightly sealing the bulb and the cap by means of a glass-like binder, and thereafter heating the mixture to reaction temperature.

2. A process according to claim 1 wherein the reaction mixture is heated by high frequency electrical wave heating.

3. A process according to claim 1, in which the mixture of substances is of such composition as to liberate vapor of one or more alkali and/or alkaline earth metals.

4. A process according to claim 3 in which at least one of the group consisting of the alloy of alkali metals, alkaline earth metals, and the alloys thereof is introduced into an airtight sealed metal capsule, the metal capsule is introduced into the interior of the bulb, and, after assemblage of the lamp the alloy is brought into contact with the interior of the bulb by melting of the metal capsule.

5. A process according to claim 1, in which said ceramic bulb is a sintered aluminum oxide bulb.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 2 3,650,593 DATED March 21, 1972 INVENTOR(S) :Bla Kerekes It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, lines 6-8, claim 1 replace "introducing an electrode and a cup containing a mixture which liberates metal vapor into a hole in a ceramic cap for the ceramic tube" with --introducing into a hole in the ceramic cap for the ceramic tube an electrode and a cup containing "a; mixture which liberates metal vapor-- Signed and Scaled this E h h a [SEAL] '8 I D of March 1983 Anest:

GERALD J. MOSSINGHOFF Arresting Offiur Commissioner of Patents and Trademarks 

1. A process of filling a lamp adapted for operation at high temperature and provided with a cylindrical ceramic bulb without an exhaust tube with the discharge substances, comprising introducing an inert atmosphere at a pressure of 20-60 mm. Hg into the bulb before sealing it from the atmosphere, introducing an electrode and a cup containing a mixture which liberates metal vapor into a hole in a ceramic cap for the ceramic tube, uniting the cap to the electrode by a glass-like binder, introducing the electrode into the ceramic bulb, airtightly sealing the bulb and the cap by means of a glass-like binder, and thereafter heating the mixture to reaction temperature.
 2. A process according to claim 1 wherein the reaction mixture is heated by high frequency electrical wave heating.
 3. A process according to claim 1, in which the mixture of substances is of such composition as to liberate vapor of one or more alkali and/or alkaline earth metals.
 4. A process according to claim 3 in which at least one of the group consisting of the alloy of alkali metals, alkaline earth metals, and the alloys thereof is introduced into an airtight sealed metal capsule, the metal capsule is introduced into the interior of the bulb, and, after assemblage of the lamp the alloy is brought into contact with the interior of the bulb by melting of the metal capsule.
 5. A process according to claim 1, in which said ceramic bulb is a sintered aluminum oxide bulb. 